Method and apparatus for recovering the refrigerant from an air conditioning system

ABSTRACT

An apparatus for recovering refrigerant ( 230 ) from an air conditioning system includes a collector for connecting hydraulically a high pressure branch and a low pressure branch, provided in the air conditioning system, with a fluid feeding duct of the fluid into the apparatus. The apparatus also has an evaporator arranged to separate the refrigerant from impurities, through an evaporation of residual liquid fractions of the refrigerant obtaining a purified refrigerant that rises towards an upper part of the evaporator, from impurities that are concentrated in a lower part of the evaporator.

FIELD OF THE INVENTION

The present invention relates to a method for recovering a refrigerantfrom an air conditioning system, for example an A/C system of cars.

Furthermore, the invention relates to an apparatus for recovering,depurating and refilling a refrigerant into said air conditioningsystem.

BACKGROUND OF THE INVENTION

As known, the refrigerant present in conditioning systems, in particularA/C systems on board of vehicles such as cars, is periodically recoveredand recycled for eliminating impurities accumulated during theoperation. A type of recovering and regenerating machine is disclosed inEP1367343A1.

Furthermore, for opposing the greenhouse effect due to the dispersion ofthe refrigerant gas used in the conditioning systems, laws andregulations define more and more restrictive limits on the waste gasrecovering processes, like for refrigerant R-134a currently known inmost of the air conditioning systems of cars. In particular, thepresently known regulations require that at least the 95.0% of the totalgas contained in the air conditioning system is recovered.

With the introduction in the new cars, for example according to the2006/40/CE regulation, of the refrigerant called HFO-1234yf, which has alower impact on global heating than HFC-134a, but a much higher cost,the step of recovering the gas becomes important concerning both theenvironmental and the economic aspects.

A further drawback concerned with the safety of the recovering andregenerating steps is concerned with the fact that refrigerant HFO1234yf is inflammable. Actually, residual fractions refrigerant presentin the system, whose recovery would require too much time, are normallydischarged in the environment when the vacuum pump of the refrigerantrecovering machines is operated. The vacuum step is a step necessarythat is done before refilling the gas. The discharge of small amounts ofrefrigerant, which then would make a mix with the oxygen present in theair, can generate a gaseous mixture capable of exploding or catchingfire, with consequent danger for objects and people.

The operations of recovering, regenerating and refilling the refrigeranteffected by machines as described in EP1367343A1 must follow particularstandards, like SAE J2843 and SAE J2788, which, beyond defining aminimum threshold recovered refrigerant (for example 95%), define alsosafety conditions and time limits for carrying out these steps. Inparticular, at least the 95.0% of refrigerant has to be recovered in amaximum time of 30 min, without heating the components of the system, inan outside temperature range between 21° and 24° C. etc.

The above described standards cannot be easily accomplished by theexisting recovering machines. A particularly disadvantageous situation,cannot fulfill such standards, occurs when the temperature around theair conditioning system is very low, at which is even difficult torecover 90% of the refrigerant. In fact, at such a low externaltemperature, the refrigerant present in the system is mainly in liquidform, and then difficult to recover.

Circuits equipped with a heating system exist, in order to assist therecovery. However, these circuits make the air conditioning system lesssafe and more expensive. Operations of heating the system are also riskyand complex, since the storage reservoir of the refrigerant of the carA/C systems are normally located in not easily accessible zones, behindthe motor.

With reference to FIG. 1, a diagrammatical view of a car A/C system 200of known type comprises a condenser 201, a filter 202, a calibrated hole203, an evaporator 204, a storage container for the refrigerant 205,which separates the liquid phase and the gaseous phase, and a compressor206. Downstream of the compressor a high pressure connection 221 isprovided, whereas on the storage container a low pressure connection 222is provided.

Presently, a machine of known type 230 (FIG. 1) for recovering andregenerating refrigerants, similar to that described in EP1367343A1, canrecover the refrigerant from a hermetic compressor 233, connected bymeans of flexible tubes that reaches collector 235 and a high pressure221 and a low pressure 222 connections to the air conditioning system.Owing to the work of the compressor 233, the refrigerant is subjected tosuction up to pressures quite below the atmospheric pressure andaccumulated after the process for regenerating in a storage cylinder234.

More precisely, when the system 200 is turned off, the liquid fractionof the refrigerant tends to migrate by the pressure difference from thehigh pressure zone 221 towards the storage container 205, runningthrough the calibrated hole 203 and the compressor 206. The recoveringof refrigerant is carried out mainly in liquid phase from the highpressure connection 221 and in gaseous phase from the low pressureconnection 222. However, in environmental conditions of low temperaturea large amount of the liquid fraction of the refrigerant is in thestorage container 205, and the step of recovering the refrigerant fromevaporation can be carried out only by remarkably lowering the suctiondepression of the machine, by the compressor unit 233. For reachingthese conditions, however, a high increase of the time for recoveringand treating the refrigerant is necessary. To the end of recovering atleast 95%, in order to meet the Regulations, the time for the recoverycan exceed 30 minutes.

The recovering and regenerating step of the refrigerant requires avacuum pump 231, which is completely separated from the compressor unit233, and which carries out the vacuum step, up to maximum vacuum gradepossible, discharging in the environment the refrigerant that was notrecoverable with the previous recovery step, and assisting the followingrefilling of regenerated refrigerant. It must be noted that the less isthe refrigerant that remains after the step of recovering, the more isrefrigerant that is discharged in atmosphere, with the above describeddrawbacks of polluting, risk of catching fire, and waste of expensiverefrigerant.

It is therefore desirable to speed up the time for emptying the airconditioning system and increasing the quantity of recoveredrefrigerant.

An expensive solution would be to use a high power compressor forcreating a maximum suction of the refrigerant in a short time. However,this solution would increase too much the costs of the machine, owingnot only to the higher cost of the compressor, but also to an overall amore robust sizing of suction system to bear the more powerful action ofthe compressor. Such solution, furthermore, would not solve completelythe above described problems, and would complicate the regenerationprocess.

SUMMARY OF THE INVENTION

It is then a feature of the present invention to provide an apparatusfor recovering the refrigerant from an air conditioning system, like anA/C system for cars, in a way that a minimum quantity of refrigerant isleft in the storage container of the air conditioning system and therecovery is as quick as possible.

It is also a feature of the present invention to provide an apparatusfor increasing the speed of the fluid through the apparatus same andthen of reducing the time necessary for regenerating the fluid.

It is a particular object of the present invention to provide anapparatus that makes it possible to obtain the above describedadvantages without however causing excessive costs for additionalimplementations.

It is also a feature of the present invention to modify an existingrecovering or regenerating apparatus without introducing heavyconstructional complications.

It is a further feature of the present invention to provide a methodthat achieves the same advantages.

These and other objects are achieved by an apparatus for recovering arefrigerant from an air conditioning system, comprising:

-   -   a collector arranged to connect hydraulically a high pressure        branch and a low pressure branch of the air conditioning system        with a fluid feeding duct in the apparatus;    -   an evaporator arranged to separate the refrigerant from        impurities through an evaporation of residual liquid fractions        of the refrigerant obtaining a purified refrigerant that rises        towards an upper part of the evaporator and impurities that are        concentrated in a lower part of the evaporator;    -   a suction unit for circulating the purified refrigerant exiting        from the evaporator, the suction unit being in hydraulic        connection with the feeding duct through the evaporator, the        suction unit comprising a compressor;    -   a condenser in hydraulic connection with the suction unit for        circulating the refrigerant, the condenser arranged to cool and        condense the refrigerant exiting from the suction unit;    -   a storage container in hydraulic connection with the condenser,        the storage container arranged to contain the refrigerant        condensed by the condenser;    -   wherein upstream of the evaporator an auxiliary compressor means        is provided arranged in parallel to the feeding duct, the        auxiliary compressor means being configured to boost the flow        rate of the refrigerant towards the evaporator and for assisting        a progressive pressure reduction of the refrigerant in the air        conditioning system in cooperation with the suction unit.

This way, the auxiliary compressor means causes the air conditioningsystem to reach quickly the low pressures that allow an almost completerecovery of the refrigerant. More precisely, the suction unit which isnormally provided for circulating the purified refrigerant, which insubstance is the compressor that is arranged downstream of theevaporator, carries out its suction function of the cooling liquid fromthe air conditioning system through the evaporator and the feeding ductcoming from the collector. The presence of the auxiliary compressorupstream of the evaporator boosts the compressor of the suction unitspeeding up the emptying steps of the system, recovering morerefrigerant possible, and reaching a maximum vacuum rate in the systemat the end of the recovery step. The recovery time can then beremarkably decreased about 30% with respect to the prior art recoveringsystems.

Advantageously, the feeding duct comprises a first portion, downstreamof the collector, and a second portion consecutive to the first portionand arranged upstream of the evaporator, and the auxiliary compressormeans is arranged in parallel to the second portion, in the secondportion a feed valve being arranged that is movable between an openposition and a closed position, in a way that, when the pressure in thefirst portion is higher than a threshold value, the auxiliary compressordoes not operate and the feed valve is in open position, and in a waythat, when the pressure in the first portion is lower than the thresholdvalue, the auxiliary compressor means is turned on and the feed valve isin closed position, causing the refrigerant to be fed to the evaporatorthrough the auxiliary compressor means, which helps to reduce furtherthe pressure on the first portion of the feeding duct in cooperationwith the suction unit.

This way, the first recovery step, i.e. when the pressure in the systemis still enough high, for example above 200 mb, can be carried out in atraditional way only by the compressor of the suction unit. Instead, forlower pressures, the feed valve is closed, and the auxiliary compressormeans is activate and contributes to reach quickly minimum values ofpressure in the system.

In a possible embodiment, the auxiliary compressor means comprises avacuum generation device. This way, once ended the recovering step of asignificant fraction of refrigerant, for example beyond 95/96% ofrecovered refrigerant, it is possible to continue the recoveryincreasing the vacuum rate in the system.

Advantageously, said vacuum generation device is connected hydraulicallywith the evaporator by a three-way valve, the three-way valve arrangedto connect selectively the vacuum generation device with the evaporator,or with a purge duct, in a such a way to allow the vacuum generationdevice to work selectively either, as auxiliary compressor means, or topurge the refrigerant that cannot be regenerated and still residuallypresent in the air conditioning system. This way, it is possible to stoprecovering the refrigerant beyond the above described significantthreshold, or an upper threshold, and purge the residual fraction,whereas in the meantime the evaporator, the compressor of the suctionunit and the condenser are completing the regeneration of therefrigerant.

Alternatively, the auxiliary compressor means for reducing the pressureof the refrigerant on the first portion of the feeding duct comprises adry-operating compressor, and wherein upstream of the dry-operatingcompressor a vacuum generation device is arranged to purge therefrigerant that cannot be regenerated from the apparatus for recoveringrefrigerant.

This way, it is possible to use a dry-operating compressor of minimumconsumption and cost, in addition to the vacuum pump normally present inthe recovery and regeneration machines of known type. The dry-operatingcompressor does not require lubrication since it exploits the lubricantalready present in the refrigerant that is subjected to suction from theair conditioning system.

According to another aspect of the invention, a method for recoveringand regenerating a refrigerant from an air conditioning system comprisesthe steps of:

-   -   feeding a refrigerant through a collector in a refrigerant        regenerating apparatus, the collector arranged to connect        hydraulically a fluid feeding duct of the apparatus with a high        pressure branch and a low pressure branch of the air        conditioning system;    -   evaporating residual liquid fractions of the refrigerant by an        evaporator arranged to separate the refrigerant from impurities        obtaining a purified refrigerant that is concentrated in an        upper part of the evaporator and impurities that are        concentrated in a lower part of the evaporator;    -   causing a suction and circulating the refrigerant through the        apparatus by a suction unit, the suction unit being in hydraulic        connection with the feeding duct through the evaporator;    -   condensing the refrigerant exiting from the suction unit by a        condenser in hydraulic connection with the suction unit for        circulating the refrigerant;    -   accumulating the refrigerant condensed by the condenser into a        container in hydraulic connection with the condenser;        whose main feature is that the suction step and the step of        circulating the refrigerant through the apparatus is carried out        by the suction unit and by auxiliary compressor means that        operate upstream of the evaporator, and that increase the flow        rate of the refrigerant towards the evaporator for assisting a        reduction of pressure of the refrigerant in the air conditioning        system.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristic and/or advantages of the method and of theapparatus for recovering and regenerating refrigerant in conditioningsystems, according to the present invention will be made clearer withthe following description of an exemplary embodiment thereof,exemplifying but not limitative, with reference to the attached drawingsin which:

FIG. 1 shows an apparatus for recovering and regenerating refrigerantaccording to the prior art, connected to an air conditioning system;

FIG. 2 shows the circuit of the apparatus for recovering andregenerating according to the prior art of FIG. 1;

FIG. 3 shows a diagrammatical view of a first exemplary embodiment of anapparatus for recovering and regenerating according to the invention;

FIG. 4 shows a diagrammatical hydraulic view of a first preferredexemplary embodiment of an apparatus for recovering and regeneratingaccording to the invention;

FIG. 5 shows a diagrammatical view of a second exemplary embodiment ofan apparatus for recovering and regenerating according to the invention;

FIG. 6 shows a diagrammatical hydraulic view of a second preferredexemplary embodiment of an apparatus for recovering and regeneratingaccording to the invention;

FIG. 7 shows a diagrammatical view of a third exemplary embodiment of anapparatus for recovering and regenerating according to the invention;

FIG. 8 shows a diagrammatical hydraulic view of a third preferredexemplary embodiment of an apparatus for recovering and regeneratingaccording to the invention.

DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

With reference to FIG. 3, an apparatus 230 for recovering andregenerating the refrigerant coming from collector 235 comprises, withrespect to the systems of the prior art of FIGS. 1 and 2, a vacuum pump231, or alternatively, a dry-operating compressor, upstream ofevaporator 232 and in parallel to feeding duct 101, in a way that, in apredetermined operative configuration, the refrigerant can cover inseries a path through vacuum pump 231, evaporator 232 and suction unit233.

Vacuum pump 231 can be excluded from the regeneration circuit orincluded in the circuit by means of valves 241 a and 241 b. Suchparticular technical solution allows vacuum pump 231 to work in thesuction step only when suction unit 233 drops below a thresholdpressure, obtaining a further reduction of the pressure in feeding duct101 and therefore in the apparatus arranged between collector 235 andsuction unit 233.

This way, differently from the prior art, for example as described forFIGS. 1 and 2, vacuum pump 231 of the system 230, or alternatively, thedry-operating compressor, according to the invention, assist theevaporation of the refrigerant, thus increasing the speed of recoveringthe refrigerant and maximizing the amount of refrigerant recovered, asdescribed above.

With reference to FIG. 4, in more detail, the feeding duct comprises afirst portion 101 a, downstream of the collector, and a second portion101 b, consecutive to the first portion 101 a and arranged upstream ofevaporator 232. This way, the auxiliary compressor means is arranged inparallel to second portion 101 b, in which feed valve 241 a is present.Such valve is movable between an open position and a closed position,and, when the pressure in the first portion 101 a remains above athreshold value, the auxiliary compressor 231, i.e. the vacuum pump ordry-operating compressor, does not operate and feed valve 241 a is in anopen position. Instead, when the pressure in the first portion 101 b islower than the threshold value, the auxiliary compressor 231 turns onand the feed valve is in closed position, so that the refrigerant is fedto the evaporator through the auxiliary compressor 231, which works, inorder to lower further the pressure on the first portion 101 a offeeding duct 101, in cooperation with suction unit 233, in the recoverywhen suction unit 233 “finds it difficult” to complete the action ofrecovery. In FIGS. 3 and 4 a safety valve 241 b is also shown which isarranged to avoid losses and leaks through the auxiliary compressor 231when feed valve 241 a is open.

In FIG. 4 parts of the recovering and regenerating circuit arefurthermore shown that are already known in the existing machines, likethe condenser, the oil separator, the collection reservoir for theresidues concentrated by evaporator 232, etc., as already described inEP1367343A1.

With reference to FIGS. 5 and 6, in an exemplary embodiment of theinvention, vacuum pump 231, beyond being arranged in order to beexcluded or included by the valves 241 a and 241 b, as already describedwith reference to FIGS. 3 and 4, can be connected hydraulically toevaporator 242 by a three-way valve 241 c. Such particular technicalsolution allows a double function to vacuum pump 231:

-   -   moving to a first hydraulic connection position of vacuum pump        231 with evaporator 232, when also valve 241 b is open, and        valve 241 a is closed, i.e. as already above described for        reducing the pressure in feeding duct 101 and therefore along        the devices arranged between collector 235 and suction unit 233,    -   moving to a second hydraulic connection position with the        environment of vacuum pump 231, for purging the not recoverable        refrigerant, when it is not advisable to continue the recovering        of refrigerant.

Three-way valve 241 c, in the second position, with valve 241 a closedand vacuum pump 231 in function, allows to continue purging andvacuuming the system, insulating at the same time evaporator 232 andsuction unit 233, which can complete the recovery up to an exhaustion ofrefrigerant in evaporator 232.

With reference to FIGS. 7 and 8, an apparatus for recovering andregenerating refrigerant comprises, with respect to the systems of theprior art of FIGS. 1 and 2, a dry-operating compressor 243 upstream ofevaporator 232 in parallel to feeding duct 101. The dry-operatingcompressor 243 is excluded from or included in the regeneration circuitby valves 241 a and 241 b, in the way described also with reference toFIGS. 3-6. Such particular technical solution allows the dry-operatingcompressor 243 to turn on only in the suction step when the pressure insuction unit 233 drops below a threshold, obtaining a further reductionof the pressure in feeding duct 101 and therefore along the devicesarranged between collector 235 and suction unit 233. This way, similarlyto the other solutions above described, the dry-operating compressor 243assist evaporating the refrigerant in the air conditioning system,increasing the speed of recovering the refrigerant and the maximumamount of refrigerant recovered.

By closing valves 241 a and 241 b and turning the dry-operatingcompressor 243 off, it is possible, in a traditional way, to operatevacuum pump 231 for purging the refrigerant that cannot be recovered,when it is not preferred continue the recovering process, by insulatingat the same time evaporator 232 and suction unit 233, which can completethe regeneration up to exhaustion of refrigerant in evaporator 232.

The solution of the dry-operating compressor 243 maximizes theefficiency of the machine with a minimum additional cost, since it is alow cost component of and it requires minimum maintenance. It does notrequire lubrication because it exploits the presence of oil in therefrigerant that is recovered from the system. Further, it normally hasnot a high vacuum tightness, and then cannot be used for vacuuming theair conditioning system, but this function is not necessary especiallywhen the vacuum pump is present, which intervenes as described above.

The foregoing description of a specific embodiment will so fully revealthe invention according to the conceptual point of view, so that others,by applying current knowledge, will be able to modify and/or adapt forvarious applications such an embodiment without further research andwithout parting from the invention, and it is therefore to be understoodthat such adaptations and modifications will have to be considered asequivalent to the specific embodiment. The means and the materials torealize the different functions described herein could have a differentnature without, for this reason, departing from the field of theinvention. It is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

1. An apparatus for recovering a refrigerant from an air conditioningsystem, said apparatus comprising: a collector hydraulically connectedto a high pressure branch and a low pressure branch of the airconditioning system with a fluid feeding duct in said apparatus; anevaporator arranged to separate said refrigerant from impurities throughan evaporation of residual liquid fractions of said refrigerant, inorder to obtain a purified refrigerant that evaporates and rises towardsan upper part of the evaporator, and to obtain impurities that areconcentrated in a lower part of said evaporator; a suction unit forcirculating the purified refrigerant exiting from said evaporator, saidsuction unit being in hydraulic connection with said feeding ductthrough said evaporator, said suction unit comprising a compressor; acondenser in hydraulic connection with said suction unit, said condenserarranged to condense the refrigerant exiting from said suction unit; astorage container in hydraulic connection with said condenser, saidstorage container arranged to contain the refrigerant condensed by saidcondenser; wherein upstream of said evaporator an auxiliary compressormeans is provided arranged in parallel to said feeding duct, saidauxiliary compressor means configured to boost the flow rate of saidrefrigerant towards said evaporator and for assisting a progressivepressure reduction of said refrigerant in said air conditioning systemin cooperation with said suction unit.
 2. The apparatus according toclaim 1, wherein said feeding duct comprises a first portion, downstreamof said collector, and a second portion consecutive to said firstportion and arranged upstream of said evaporator, and said auxiliarycompressor means is arranged in parallel to said second portion, whereinin said second portion a feed valve is arranged movable between an openposition and a closed position, so that, when the pressure in said firstportion is higher than a threshold value, said auxiliary compressormeans is turned off and said feed valve is in open position, and sothat, when the pressure in said first portion is less than said value,said auxiliary compressor means is turned on and said feed valve is inclosed position, so that the refrigerant is fed to said evaporatorthrough said auxiliary compressor means, which cooperates with saidsuction unit for lowering further the pressure on said first portion ofsaid feeding duct.
 3. The apparatus according to claim 2, wherein saidauxiliary compressor means for lowering the pressure of said refrigeranton said first portion of said feeding duct comprises a vacuum generationdevice.
 4. The apparatus according to claim 3, wherein said vacuumgeneration device is connected hydraulically with said evaporator by athree-way valve, said three-way valve arranged to connect selectivelysaid vacuum generation device with said evaporator, or with a purgeduct, in order to cause said vacuum generation device to workselectively either as auxiliary compressor means or as purge means, forpurging the refrigerant that cannot be regenerated and still residuallypresent in said air conditioning system.
 5. The apparatus according toclaim 2, wherein said auxiliary compressor means for reducing thepressure of said refrigerant on said first portion of said feeding ductcomprises a dry-operating compressor, and wherein upstream of saiddry-operating compressor a vacuum generation device is arranged to purgethe refrigerant that cannot be regenerated from said apparatus forrecovering refrigerant.
 6. A method for recovering and regenerating arefrigerant from an air conditioning system, said method comprising thesteps of: feeding a refrigerant through a collector into a recoveringand regenerating apparatus, said collector arranged to connecthydraulically a feeding duct of said apparatus with a high pressurebranch and a low pressure branch of said air conditioning system;evaporating residual liquid fractions of said refrigerant from anevaporator arranged to separate said refrigerant from impuritiesobtaining a purified refrigerant that evaporates rising towards an upperpart of the evaporator and obtaining impurities that are concentrated ina lower part of said evaporator; causing a suction and circulation ofthe refrigerant through the apparatus by a suction unit, said suctionunit being in hydraulic connection with said feeding duct through saidevaporator; condensing the refrigerant exiting from said suction unit bya condenser in hydraulic connection with said suction unit; accumulatingrefrigerant condensed by said condenser into a container in hydraulicconnection with said condenser; wherein said step of causing a suctionand circulation of the refrigerant through the apparatus is carried outby said suction unit in combination with an auxiliary compressor meansthat operates upstream of said evaporator, and that increases the flowrate of said refrigerant towards said evaporator for assisting areduction of the pressure of said refrigerant in said air conditioningsystem.